Astigmatic dial



Patented Sept. 9, 1924.

UNITED STATES PATENT 'OFFICIEL assurer/tario DIAL.

vApplication led August 2, 1922. Serial No. 579,235.

To all whom it may Concern.'

Be itlrnown that I, IVILLIAM P. Rnavns, a citizen of the United States, residing at Greensboro, county of Guilford, and State of North Carolina, have invented certain new and useful Improvements in Astigmatic Dials, of which the following is a specification. l,

The present invention relates to eye testing apparatus and particularly to devices of the meridian dial type designed to determine the axis of astigmatism of the eye in its different meridians.

In my copending application Ser. No. 558,493, filed May 4, 1922, is disclose-d and claimed an eye testing apparatus in which the meridian lines may be varied in thickness as desired, thus avoiding the necessity for using a series of charts having lines inscribed thereon, the lines of the several charts being of different values asmeasured in visual acuity units.

The object of the present-invention is to provide an improved apparatus of the type disclosed in the application above mentioned. In my prior device the meridians comprise a series of blades radiating from a common center and having rectangularv cross sections, together with means for simultaneously rotating the blades, the blades appearing as Aline lines when their edges are 'presented to the observer and as relatively broad lines when the sides of the blades are visible to the observer.V Unless considerable care is taken withY the placing of the apparatus'with respect to the daylight through Windows or doors or artificial light in the room,'it is possible for the blades at some point of their rotation to rellect said lights from the blades to the eye of the observer, which will give a dilerent color value to the blades rellecting thelight. The improved apparatus of the type disclosed also prevents the halation of light especially in the background which gives a differentcolor value to the blades. It is the object of the present invention to provide a meridian dial which embodies the same principle as that disclosed in my co- Contact with each other, to a position in which they make equal angles withl the ob;

servers line of vision, the result being that the observer` looks into a V-shaped groove ing drawings one form is illustrated by wayv of example and will be described in detail.

In the drawings:

Fig. 1 isa front elevation of the appara-` tus the blades being adjusted to appear of minimum size;

Fig. 2 is a' similar view of portion of thel apparatus showing the blades adjusted to appear of maximum size;

Fig. 3 is aside elevation of'portion .ofthe blade operatingmechanism;

Fig. 4 is a section on line 4-4 of Figure 1 to a larger scale; andV y A Fig. 5 is al section on line 5-.-'5 of Figure 4 showing in full and dottedlines the extreme blade'positions.

Thev frame Aof the dial comprises essentiallythree semi-circular concentric .members V10, 11 and 12 securedtogether by cross mem-V bers 13 and 14 at their lower'ends. vThe blades are disposed between members 10 and 11 and radiate from a single central point 15, being spaced at intervals of 5 of arc Each blade comprises two# portions 16 and 17 substantially equal ink from each other.

length and in y.cross section, one blade portion being, however, somewhat broader than the other, as shown in Figure 5. Blade portion 16 has its ends securedvto spindles 18 and blade portion 17has its ends secured to bushings 19, the spindles 18 being rotatably l supported in bushings 19, and the bushings 19 being rotatably supported in the frame members 10 and 11. Integral with each upper bushing 19 is a gear segment 20, and secured to the upper end of each spindle 18, by means of an adjusting screw 21, is a second gear segment 22. From Figure 3 it will be seen that these gear segments are so cut away that they may be rotated relatively to each other through substantially an angle of As each gear segment is connected to a blade portion it follows that the blades may be swung apart until they make substantially an angle of 90 with each other, y

as shown in dotted lines in Figure 5, or may be folded against each other, as shown in full lines in this igure.

For eecting the simultaneous rotation of the blades a slotted semi-circular member 23 is provided having oppositely directed sets of teeth 24 which constitute racks engaging the respective segments and 22. Member 23 is secured to frame member 11 by bolts 25, these bolts however, passing through slots 26 in member 23 so that the latterinay be longitudinally adjusted. Rotatably secured in the Jframe is a shaft 28 having mounted thereon a dish 29 provided With a cam slot 30 through Which extends a pin 3l secured to the rack member 23. A handle 32 is provided :for rotating shaft 28 and it Will be seen that rotation of this shaft Will effect movement `of the rack member 23 and hence swinging of the blade portions.

In use the dial is usually placed in front of an illuminated field, which `eld lmay be artii'icially illuminated or may be a natural field such as the sky. The observer is so placed that he looks into the grooves Aformed When the blade portions are :swung apart, Which f grooves appear perfectly black, vit being impossible for the light coming from behind the dial to be reflected from the inner surfaces of thefblades and hence there is no possibility of there being any variance in color between the several blades.L p

To one skilled in the art will .be 'tapparent that the invention maybe carried vout in various forms of apparatus and is not limited to the enact form, shown ,and described.

Having thus described my'invention, What I claim as new and desire vto secure by Letters Patent is: K l' y y l. An astigmatic dial.including in comfbination, ay support, a plurality of blades, mounted on 'the `support. and radiating from a common center, the blades being formed in r portions relatively `movable to cause them to appear to an observer as lines which vary 1n Width.

2. An astigmatic dial including in` cornbinaton, a support, a plurality of blades, mounted on the support and radiating trom a common center, each blade being formed in tivo portions openable and c-losable to cause them to appear to an observer as lines which vary in Width.

3. An astigmatic dial including in conibination, a support, a plurality of blades, mounted on the support and radiating from a common center, each blade being divided longitudinally into two parts, relatively rotatable substantially about a common axis, to cause it to appear to an observer as a line of varying `Width.

4. An astigmatic dial including in combination, a support, a plurality of blades, mounted on the support and radiating from a common center, the blades being formed in portions' relatively movable te cause them to appear to an observer as lines Which vary in Width, and means mounted on the frame for rotating said blades.

5. An astigmatic dial including in combination, a support, a plurality of blades, mounted on the support and radiating trom a common center, each blade being divided longitudinally into two parts each part oit rectangular cross section, and the tivo Vparts being relatively rotatable, so that they mayl be caused to appear to an observer as lines ofvarying Width.

5. Eyetesting apparatus including in combination, a support, a blade `mounted on the support and Iformed in two portions, operw able and closable to cause the blade to `appear to .an observer as a line of varying Width.

7.. Eyetesting apparatus includingfin com-` signature.

IVILLIAM P. REAVE S.. 

